PSI - Issue 52

Thi Ngoc Diep Tran et al. / Procedia Structural Integrity 52 (2024) 366–375 Thi Ngoc Diep Tran/ Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 6. (a) Fitted ellipses to particles; (b) Relative frequency of elliptical approximations and particles according to particle ’s length .

To investigate the influence of circular particles on crack propagation, four models with variations in particle distribution and particle size are presented: original model (model 1), model with circles arranged in an aligned arrangement (model 2), additionally with an increased radius (model 3) and clusters of large circles (model 4) as shown in Fig. 7. The simulation results show that the cracks are propagated horizontally in aligned particle models compared to the origin model. The start of the crack and corresponding crack-inducing particle in the model has been localized and marked in Fig. 7a. Crack initiation is characterized by the detached particle-matrix interface and then grown around the particle. This implies that a particle with higher aspect ratio would deflect the crack, and hence deviates from its path (Ayyar and Chawla (2006)). Crack initiation tends to occur on large radius circles, which is clearly shown in model 3 and model 4. Comparing the tensile strength of the four models in Fig. 7b, it can be seen that model 2 with aligned circles has the maximum tensile strength, meanwhile, the large radius circles in model 3 and model 4 cause lower tensile strength.

Fig. 7. (a) Crack propagation in models with circular particles; (b) Calculated normalized tensile strength of models with circular particles.

4.2. Models with various particle shapes In the next investigation, six models with various particle shapes are carried out: an original model obtained from micrograph (model 1), one with added large particles (model 2), one with circular (model 3) and elliptical particles (model 4), one with sharp-edged particles (model 5), and one with aligned particles (model 6). As shown in Fig. 8, the crack propagates differently in each model, whereby the crack initiation tends to start at long and horizontally oriented particles. As described in the last section, the crack path was deflected by the large particles. This effect can be clearly observed in models 5 and 6. Crack growth in models 2, 3, and 4 is more significant than in other models, since the crack path almost propagates through the specimen. This observation can be verified by the normalized stress-displacement curves in Fig. 9. The tensile strength of models with large particles, circles, and ellipses are the lowest and do not differ much from each other. The model with particles arranged in an aligned arrangement again has the highest tensile strength, followed by the original model and model with sharp-edged particles. It can be seen that in the original (model 1) and the model with sharp-edged particles (model 5), the sharp edges are oriented in the